route53dyndns

I am a small set of scripts to dynamically update a given domain name record on Amazon Route53 service based on the current IP address of a gateway (see my change_ip.sh script).

I can be used as a docker container, either running 24/7 or by having /change_ip.sh as entrypoint or command. My docker entrypoint is a permanent loop that launches /change_ip.sh script every minute. To avoid incurring AWS cost by using the API, I have a very basic change detection:

• I store last known ip from AWS on /var/lastip (or 0.0.0.0 to force running the script)
• I compare the gateway's ip with the one stored
• If the IPs are not equal, I call AWS Route 53 to update the DNS with the actual public IP obtained (check route53.py)
• If they are equal, I do not call AWS at all.
• Every 60 cycles, I force a refresh (around every hour) by force updating /var/lastip with 0.0.0.0

Additional information:

• change_ip.sh contains a couple of ways of obtaining the IP address
• route53.py is a small python script using boto3 to update a set of given DNS records (MX, TXT, A... whatever).
• The following dependencies are expected:
  • change_ip.sh (using ssh to connect to your router)
    • Environment variables
      • $GW_USER User for connecting to the gateway (additionally, use .ssh/config)
      • $GW_IP IP Address from your gateway
    • /root/.ssh configuration (keys, known hosts, etc)
      • Can be mounted as a docker volume (see dockerfile)
  • route_53.py
    • Environment variables
      • AWS_ROUTE53_ZONES a python-compatible list of pairs, with [(zone_id,zone_name),...] format
      • AWS_ROUTE53_A_RECORD a DNS A type record to look for ip changes (i.e. dynip if you have dynip.yourdomain.com) This is to avoid changing several records at once. A good idea is to have a single A record and then as many CNAME records you need pointing to that A record
      • Uses python get_docker_secret to read the secrets either from docker secrets exposed file (usual location) or from environment. Be aware that docker secrets need docker swarm. Use env. variables if you don't have a swarm. The docker secrets variables used are the standard AWS credentials environment variables:
        • AWS_ACCESS_KEY_ID
        • AWS_SECRET_ACCESS_KEY
  • entrypoint.sh just forces a permanent loop ensuring AWS is called at least every hour.